Peake told the Associated Press that one of the biggest
challenges of running a 26.2-mile race on the International Space
Station is the harness he wears to keep his feet on
the treadmill in weightlessness, which rubs his shoulders and
waist.

"It's a great challenge that I set myself, and I'm quite
glad this is happening later on in the mission," Peake told the
AP.

Peake, who arrived at the ISS in December, told the
publication that he wants to finish the marathon in under 4
hours.